Hydrogenation of aromatic hydrocarbons using cobalt hydrogenation catalysts



United States Patent HYDROGENATION 0F AROMATIC HYDROCAR- BONS USING COBALT HYDROGENATION CAT- ALYSTS Stephen M. Kovach, Highland, Ind., assignor to Sinclair Research, Inc, New York, N.Y., a corporation of Delaware No Drawing. Filed Mar. 24, 1964, Ser. No. 354,467 6 Claims. (Cl. 260-667) The present invention relates to the hydrogenation of sulfur-containing aromatic hydrocarbons. In one aspect the invention is directed to aromatic hydrocarbon feed compositions of enhanced susceptibility to hydrogenation when converted in the presence of cobalt hydrogenation catalysts. In another embodiment the invention is directed to a method for accelerating the hydrogenation activity of cobalt hydrogenation catalysts in the hydrogenation of aromatic hydrocarbons, particularly polynuclear aromatic hydrocarbons.

This petroleum refiner is continually seeking new and better processing schemes for the conversion of the heavy ends of petroleum crude oil to more useful lower boiling products and/or products of improved quality. Among these conversion processes are catalytic hydrotreating which includes hydrogenation, for instance, of the aromatics and olefins contained in petroleum fractions, hydrodesulfurization, hydrocracking, etc. A variety of catalysts are employed in these hydrotreating reactionstwo of the most popular types being solid cobalt catalysts and nickel catalysts. Of the two types, the nickel catalyst is the much better hydrogenation catalyst, the relative hydrogenation activity of the cobalt-containing catalyst being poor in comparison, while the cobalt catalyst, on the other hand, is by comparison the better hydrodesulfurization catalyst.

It has now been discovered that the activity of a cobalt hydrogenation catalyst in the hydrogenation of normally liquid aromatic hydrocarbons can be signif icantly increased by conducting the reaction in the presence of a small amount of particular sulfur compounds. While the sulfur compounds of the invention enhance the hydrogenation activity of cobalt catalysts they actually poison the activity of nickel catalysts. This is an unusual phenomenon, for most hydrogenation accelerators increase the activity of the hydrogenation catalysts alike.

The sulfur compound which when added to an aromatic hydrocarbon feed provides a composition having en hanced susceptibility to hydrogenation in the presence of a cobalt hydrogenation catalyst is an aromatic sulfide having two aromatic nuclei interconnected by at least one sulfur atom. Stated otherwise, the additive of the present invention is a sulfur compound in which the bonds of the sulfur atom are each attached to an aromatic nuclei. The aromatic nuclei of the additive can be unsubstituted or substituted with groups that do not unduly, deleteriously interfere with the hydrogenation enchancing function of the sulfur compound and also can be partially hydrogenated if desired. Generally, the diaromatic hydrocarbon sulfides will have about 12 to 24 carbon atoms, preferably 12 to 16 carbon atoms. Compounds wherein more than one sulfur atom bridges the aromatic nuclei as, for instance, in the compound thianthrene, are included as well as compounds wherein the aromatic rings are directly connected as well as connected by a S-atom. The aromatic nuclei are preferably benzene or substituted benzene nuclei but one or both of the aromatic nuclei can be polynuclear, as long as the sulfur compound is soluble in the aromatic hydrocarbon feed to which it can be added. Examples of suitable sulfur compounds are diphenyl sulfides, alkyl diphenyl sulfides, dibenzothiophene, thianthrene, alkyl-substituted thianthrene and the like. The amount of sulfur compound added to the aromatic hydrocarbon will vary depending upon the particular aromatic hydrocarbon to be hydrogenated. In all cases, however, the amount added will be an effective amount and will usually provide about .00l% to 5% by Weight, preferably about 0.01% to 1% by weight, of sulfur on the basis of the aromatic feed.

The aromatic hydrocarbon feed which is hydrogenated can be a liquid aromatic hydrocarbon per se or in admixture with other liquid hydrocarbons. Although feeds wherein the aromatics are say down to about 20% by weight, are contemplated, the invention has perhaps its greatest utility with aromatics containing petroleum fractions which contain at least about 30% by weight aromatics. Special advantage is offered by the present invention when treating polynuclear aromatic hydrocarbons, such as the alkylated fused ring aromatics exemplified by methylnaphthalene, methyl tetralin, etc. found in petroleum feedstocks such as the cycle oil obtained from catalytic cracking processes.

The catalyst employed in the hydrogenation is a solid cobalt-containing hydrogenation catalyst. The cobalt catalyst can also be promoted by other active hydrogenation components as, for example, molybdenum, tungsten, etc. and is preferably supported in minor amounts on a suitable carrier such as activated alumina, silica, silica-alumina, magnesia, titania, zirconia, etc. The preferred hydrogena tion catalyst is cobalt oxide and molybdenum oxide (or the corresponding sulfides of these metals) on an activated alumina support. These catalysts usually contain about 1 to 10% by weight cobalt and, if present, about 8 to 24% by weight molybdenum on alumina and can be prepared -by known methods. It is preferred that the catalyst be sulfided before use, for instance, by treatment with H S at high temperatures to put the cobalt and other pro moting metals in sulfided form; however, the cobalt oxide form, including, for instance, cobalt molybdate, may be used and the sulfur component of the hydrocarbon stream being treated will sulfide the catalyst. In fact in most cases, the aromatic feedstock will contain a significant amount of naturally occurring sulfur compounds.

The hydrogenation of the aromatic hydrocarbon feeds of the invention can employ reaction conditions which I may vary over wide ranges depending on the particular feed and the extensiveness of the hydrogenation desired. Generally, the hydrogenation temperatures can vary from about 400 to 800 F. or more, while pressures can range from atmospheric up to 2500 p.s.i.g. or more, preferably about to 1500 p.s.i.g. Elevated temperatures and pressures are preferred, with temperatures of about 500 to 700 F. and pressures of about 500 to 1500 p.s.i.g. being particularly effective for the hydrogenation of polynuclear fused-ring aromatic hydrocarbons. Sufficient molecular hydrogen should be present to provide the degree of saturation desired in the aromatic compound being hydrogenated. In general, an excess of hydrogen will be used, usually about 2 to 15 moles of hydrogen being supplied per mole of feed. Either a liquid or vapor phase, reaction can be employed but the liquid phase reaction is preferred.

The following example is included to illustrate the present invention:

Example Three grams of the catalyst defined in the table below were crushed and screened to 30 mesh or finer and placed in a 300 cc. magnadrive packless autoclave. The catalyst was pretreated by evacuating the autoclave with house vacuum and pressuring with 250 p.s.i.g. hydrogen sulfide for about minutes at room temperature with stirring (600 rpm). The system was depressured to p.s.i.g. hydrogen sulfide and heating started with stirring. The temperature was raised from room temperature to 600 F. overnight (16 hours). At this point, the stirring was stopped, hydrogen was admitted to a total pressure of 1000 p.s.i.g. and milliliters of alpha methyl naphthalene containing 0.2% of sulfur as the compound identified in the table below. The system was such that a continual pressure of 1000 p.s.i.g. of hydrogen was on the contents of the bomb at all times. At intervals of 30 minutes or multiples thereof, a small sample (2-3 milliliters) was withdrawn from the bomb and a refractive index taken of the sample. When the refractive index of the sample reached 1.5800, representing approximately 50% hydrogenation to the tetralin stage the heating, hydrogen and stirring were shut off and the bomb allowed to cool to room temperature. Decalin production was checked by gas chromatography but none was found in the runs. The bomb was dismantled and the hydrocarbon separated from the catalyst by filtration. For comparison, runs were included wherein alpha methyl naphthalene was hydrogenated in the presence of each of the three catalysts but without addition of a sulfur compound to the feed. The results of the hydrogenations are summarized in the table below.

TABLE The data of the table show that thionaphthene has very little etfect on the hydrogenation activities of the cobalt and nickel catalysts. Thionaphthene and alkyl thionaphthene are the common aromatic sulfur compounds present in aromatic fractions and petroleum stocks boiling in the alpha methyl naphthalene range. However, as the data demonstrate, when a thianthrene or diphenylsulfide was utilized the hydrogenation activity of the nickel catalysts were decreased and the hydrogenation activity of the cobalt catalyst increased.

It is claimed:

1. A method for accelerating the hydrogenation activity of a solid, cobalt-containing hydrogenation catalyst in the hydrogenation of a liquid aromatic hydrocarbon which consists essentially of hydrogenating said aromatic hydrocarbon in the presence of said catalyst and a small, effective amount of a soluble aromatic sulfide having two aromatic hydrocarbon nuclei interconnected by at least one sulfur atom.

Z. The method of claim 1 wherein the amount of aromatic sulfide provides about 0.01 to 1% sulfur.

3. The method of claim 1 wherein the aromatic hydrocarbon is a polynuclear fused ring aromatic hydrocarbon.

4. The method of claim 1 wherein the sulfur compound is thianthrene.

5. The method of claim 1 wherein the sulfur compound is diphenylsulfide.

6. The method of claim 1 wherein the catalyst is a sulfided cobalt-molybdenum on activated alumina catalyst.

Conditions: 600 F., 1,000 p.s.i.g., 1,000 r.p.n1. stirring, 3 g. catalyst. Feed: 05 ml. alpha methyl naphthalene, -0.46% S as thionaphthene.

Catalyst 2.7% COO-12% 4% Ni-16% 3% Ni-12% Moo /A1 0 MOO/A1203 MOO/A1203 Time for 50% hydrog. in min., Sulfur Con1p0und0.2% Feed:

None 102 122 Thianthrene 123 166 Thionaphthene 145 142 Dipheuyl Sulfide 124 152 140 References Cited UNITED STATES PATENTS 1,965,956 7/1934 Dunkel et al 260667 1,999,738 4/1935 Pier et a1. 260667 2,481,921 9/1949 Gwynn 260667 2,736,689 2/1956 Stuart 260667 2,985,580 5/1961 Heinemann 208264 3,167,497 1/1965 Solomon 208264 OTHER REFERENCES Chemistry of Organic Sulfur Compounds in Petroleum and Products; TP 690, N 33, 1957, pages 69-72 and 77- DELBERT E. GANTZ, Primary Examiner.

S. P. JONES, Assistant Examiner, 

1. A METHOD FOR ACCELERATING THE HYDROGENATION ACTIVITY OF A SOLID, COBALT-CONTAINING HYDROGENATION CATALYST IN THE HYDROGENATION OF A LIQUID AROMATIC HYDROCARBON WHICH CONSISTS ESSENTIALLY OF HYDROGENATING SAID AROMATIC HYDROCARBON IN THE PRESENCE OF SAID CATALYST AND A SMALL, EFFECTIVE AMOUNT OF A SOLUBLE AROMATIC SULFIDE HAVING TWO AROMATIC HYDROCATION NUCLEI INTERCONNECTED BY AT LEAST ONE SULFUR ATOM. 